Vaccine Development: How Scientific ... - Semantic Scholar

YALE JOURNAL OF BIOLOGY AND MEDICINE 87 (2014), pp.519-525. Copyright © 2014.

FOCUS: VACCINES

Vaccine Development: How Scientific Collaboration and Communication Help Prevent the Spread of Disease An Interview with Erol Fikrig, MD Audrey Turchick* and Jen Czochor

Department of Genetics, Yale University, New Haven, Connecticut

In this interview, Dr. Fikrig discusses his background and interest in the molecular pathogenesis of infectious diseases. He shares with us a unique story about the development of the Lyme disease vaccine and the hurdles that arose during this process. Additionally, he comments on the current status of vaccination in the United States and what struggles remain in educating the public on the benefits of such preventive measures.

Erol Fikrig, MD, is a Waldemar Von Zedtwitz Professor of Medicine in Infectious Diseases, as well as a Professor of Epidemiology (Microbial Diseases) and Microbial Pathogenesis at the Yale School of Medicine. Dr. Fikrig received both his BA and MD from Cornell University. From there, he was an Internal Medicine resident at Vanderbilt University Hospital, and then completed a fellowship in Infectious Diseases at Yale University. Dr. Fikrig now is a senior research scientist at Yale, where he acts as a Howard Hughes Medical Institute investigator and Section Chief for Infectious Diseases. Over the course of his career, Dr. Fikrig has had a broad impact on our understanding of Lyme disease and played a key role in the development of the first and only Lyme disease vaccine to be brought to market. Currently, his laboratory focuses on studying vector-borne diseases such as Lyme disease, human granulocytic ehrlichiosis, and West Nile virus.

It seems like your interest in microbiology was really sparked when you were visiting Brazil while you were a medical student at Cornell. Could you give us a little background as to how you got on this path and how this drove your career in regard to vaccines? Certainly, medical school is important, but when I was in college, I was a chemistry major, and one of our projects for my thesis was to work on ways to help bacteria eat oil.

*To whom all correspondence should be addressed: Audrey Turchick, Department of Genetics, Yale University, 333 Cedar St., New Haven, CT 06520; Tele: 203-737-2787; Email: [email protected]. Keywords: vaccines, Lyme disease, tick, OspA, immunity, infectious disease, vectorborne disease 519

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Turchick and Czochor: An interview with Erol Fikrig, MD

So I was interested in bacteria in college. I didn’t get very far with that, but the purpose was to make oil-eating bacteria that could clean up spills. So that sparked my interest in microbiology, and then in medical school, I was fortunate enough to be in a place where there was a group working on projects in Brazil. I was always interested in tropical medicine and diseases transmitted by bugs, for some reason, maybe just because I had been bitten, and everyone has been bitten by mosquitos, and so forth. So they had a project in Brazil studying a disease called mucocutaneous leishmaniasis, which is a parasite that is transmitted by a sand fly and causes nasty disease. There are different types of leishmania. The mucocutaneous leishmaniasis goes to your mucous membranes and erodes them so people will lose their nose and other parts of their body where a mucous membrane is very important. It’s very disfiguring. There is no good treatment for it. The treatment today is the same as the treatment 75 years ago, which is intravenous heavy metals, pentavalent antimony. Our goal was to understand, as farmers cleared the forest in Brazil and came in contact with sand flies, how often did they get the disease, who got the disease, and what could you do about it. I worked there for the summer of my second year of medical school and my fourth year of medical school for my elective time. I think I spent about 4 to 6 months in Brazil. It was an eclectic group of people, a combination of physicians, scientists, entomologists, and field ecologists all working together. I found that cohort very stimulating — people with different expertise studying different things. I thought at that time that I might like to go into infectious diseases as a subspecialty, although I wasn’t really sure yet. So then I went to training in medicine, and then I trained in infectious diseases. I did my fellowship in infectious diseases here. At that time, Yale had just recruited a new chair of immunobiology, Richard Flavell, who was just starting his laboratory. I talked with a professor in medicine named Fred Kantor, who was an immunologist. The two of them were interested in studying Lyme disease. There was another individual in comparative

medicine, Steve Barthold, who was an animal modeler. Fred [Kantor] was interested in human Lyme disease and clinical Lyme disease. Richard [Flavell] was interested in the molecular biology of vaccine development and the immunopathogenesis of disease. Steve Barthold had developed a mouse model and was interested in modeling disease. I was very fortunate that when I was looking for a postdoc, the stars sort of aligned so that the three of them were beginning to interact. They had not interacted before, and they needed a postdoc to do the work. So I became that person. Like much of science, luck is important. Timing is important. I was very fortunate in that regard that I had those three individuals. I worked primarily in Richard Flavell’s laboratory, but I had three people who were involved in my project and who I worked with closely. And just like my time in Brazil where I had different people working with me with different backgrounds, I liked the fact that Richard [Flavell] and Steve Barthold and Fred Kantor all had different backgrounds. Our goal was to develop a vaccine for Lyme disease, and the studies that we performed in mice were very promising, and that led, not just our group but many other groups in the U.S. and elsewhere, ultimately to a human vaccine in 1998.

So you were part of the first Lyme disease vaccine. Could you talk to us a little bit about the process of developing this vaccine and how your approach might have been different from traditional approaches?

All vaccines begin with an idea and then some proof of principle, either in vitro or in vivo in an animal model. The question we first ask for any vaccine is “what is the antigen that is on the pathogen that is important for protection?” Since Borrelia is an extracellular pathogen and it lives in the connective tissue matrix, we reasoned that antibodies were very important in killing it. Complement antibodies bind the surface, complement binds, cell lysis [occurs]. So we were looking for outer surface proteins. We had several candidates, and one that we


worked on called OspA — the first one is A — was identified initially by other individuals, but we cloned it, expressed it, and purified it and made it in recombinant form. Steve Barthold had the mouse model, so rather than do it in in vitro studies, we actually went straight to a mouse model and did two things: passively transferred antibody to a mouse and actively immunized mice. We were very fortunate that in our first experiments, we were able to show full protection in the mouse model. This also goes back to the luck point, although I wouldn’t call it a lucky experiment; it was a fortunate experiment. When you do a vaccine experiment, you immunize with X amount of antigen to elicit an immune response, and you also challenge with X amount of organism. We chose a dose of organism that was 10 to the 4th, 10,000 bacteria, and we immunized with quite a robust amount of the protein and elicited a very strong antibody response. It turns out that when you do an experiment with 10 to the 4th organisms, which we did, it was fully protective. If you do that same experiment with 10 to the 7th organisms, there’s no protection. So if we had done our first experiment with 10 to the 7th organisms, we might have said it had a negative result and just gone on to other antigens. We were fortunate enough to get that result. The question is: Lyme is a tick borne disease, so what is the volume transmitted in a tick? That really becomes a critical question. But we didn’t actually think about that question. So while that first experiment is a bit of luck, it’s the animal model that makes it possible. And then how do you develop a vaccine after the animal model? After you get that initial result, there are two ways to go. One is to determine the mechanism of action of the vaccine. How does it work? That’s more of what I would call a scientific endeavor. Some of it is mundane science, some of it is actually quite complicated science. It turns out that for various reasons, this vaccine works by killing the bugs inside the tick. Another thing we didn’t know when we began is that OspA is not expressed by spirochetes inside you. They’re expressed by spirochetes inside the tick.

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When a tick takes a blood meal, spirochetes turn off that OspA protein. So spirochetes coming into your skin are in an OspA negative state. We also didn’t know that the blood meal goes into the tick, and it takes about 48 hours for the spirochetes to be transmitted from the tick to the skin. During that time period, the spirochetes remain dormant in the midgut, for the most part, and those antibodies essentially attack what I would call the couch potato-like spirochetes on the gut before they’ve had a chance to become activated and turn off the OspA protein. We actually found out all these things later in a series of rather complicated, detailed experiments, but if we had known all those things beforehand, we might not have even tried OspA as a vaccine candidate. It turns out that the things you would think make OspA a bad vaccine candidate make it a great candidate. Take evolution. When a bug infects you, and you develop an immune response to it, what does the bug do? The bug mutates, right? Look at influenza: great surface protein diversity. Most viruses and a lot of bacteria develop surface protein heterogeneity and diversity because they are being attacked by human antibodies and there is selective pressure all the time. OspA is only expressed inside a tick. It’s not expressed in you, so the spirochete hasn’t evolved; it hasn’t developed great diversity in OspA. There’s some, but not great diversity. So the things that you think might make it a bad vaccine candidate actually make it a great vaccine candidate because it’s been highly conserved among spirochetes in the U.S. I’m not saying there is no OspA variability, but it’s there for different reasons. It’s not there for selective pressure. So those are the mechanistic aspects of the vaccine that has been worked on by many groups, including us, for quite a few years. It actually turned out that when we first published our paper on the OspA vaccine, there was no tick involved. It was a syringe challenge. Several very well-respected entomologists read our paper and said, “This is baloney, they didn’t test it against tickborne disease.” And actually, we didn’t test it against tick-borne disease, and we didn’t

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even think about it as a question. It didn’t occur to us that it could be different. Tick saliva has many properties. Ticks are not just syringes. So after the entomologists wrote these comments, mostly in the New York Times, we called Andy Spielman at Harvard and his colleague Sam Telford and said, “We never thought of these points. They are good points. We don’t know anything about ticks. Would you do these experiments with us?” And they said yes. Sam Telford, who is my very good colleague now, came down, and together we performed the experiments. It turned out that the tick wasn’t an issue, and with Sam’s help we proved that the spirochete actually got killed inside the tick. Good scientific criticism is very helpful. It opens your mind to things you didn’t think about before. So that’s all mechanism, and that’s been going on for a long time. In some ways, it’s still going on because there are many things that still need to be thought out about the tick and the bug. Then there is what I would call more developmental science. Something works in a mouse, what do you do from there? There are two ways to approach that. Okay, it worked in a mouse, let’s show that it works in a hamster. Let’s show that it works in a rabbit. Let’s show that it works in a dog. Let’s show that it works in a monkey. Let’s show that it works in a human. So you can go through all these intervening steps, and frankly, many groups around the United States and around the world did many of those intervening experiments. We didn’t do many of those; we let other groups do the vast majority of them, and all those studies more or less showed the same thing: OspA was protective. Now, some of them showed 100 percent protection, some showed 50 percent protection, some 75 percent. Again, the dose is different, the way you give it — there are many ways you get different degrees of protection. But I would say there was an overall consensus that yes, this had some protective capacity, which was very reassuring. But when push comes to shove, do all those experiments help you say that this is going to be safe in a human? The answer is no. It’s not clear to me that if some-

thing works in a mouse, whether all those intervening animal steps, other than providing more data to showing something works, will help you in terms of whether it work in a human. I’m not sure you need all those intervening steps to test something in a human. Having said that, again, once you get to those points, at least for me, that’s not the type of work that a university is good at doing nor should they really be good at doing. So what happens is pharmaceutical companies become involved, and Yale has an Office of Cooperative Research, so they are involved in technology transfer. They set up meetings with various companies, and ultimately GlaxoSmithKline — it was called SmithKline Beecham at that time — developed a licensing agreement with Yale. We worked with them and helped them develop their vaccine, as did other groups. So the human stuff was done by them. That’s quality assurance, making a nice purified recombinant protein that doesn’t have toxins, no byproducts from bacteria or yeast, or however they make it. Then you test it in phase 1, phase 2, and phase 3 clinical trials. The company sponsors those trials, which are then done by academic groups and usually in a double-blinded fashion to test safety, and ultimately phase 3 is efficacy. So that’s company-sponsored work. What hurdles do you think remain for bringing a vaccine for Lyme disease back to the market?

So that goes to the question of why it was taken off the market. The short answer is, I don’t know for sure, but the company mostly says it’s due to poor sales. Take some other diseases that you have vaccines for: hepatitis B, tetanus, measles. You’ve probably had those vaccines. Those diseases can kill you, right? Lyme disease, for the most part, is not a life-threatening disease, and it’s also a treatable disease and, except in a small number of cases, the symptoms are usually not extremely severe: perhaps a skin rash, a fever, a sore joint. There are some complicated symptoms like a slow heart rate or meningitis, which are very concerning, but most of the disease is an early


skin rash. So since it’s eminently treatable and not life threatening, maybe the market was not as great as it would be for another disease. For example, if you had a vaccine against HIV, if there were some side effects from an HIV vaccine, it would still be pretty useful. But for a vaccine like this, you really want to have zero side effects. So there was a high bar to cross for people to take it. I don’t think that would change for another Lyme vaccine.

You have a recent study about the presence of Lyme disease in certain areas versus others, and you talk about the microbiota of the gut of the tick affecting spirochete colonization. Do you think that perhaps trying to get a vaccine off the ground in certain regions would be better if you could predict which areas would need the vaccine more than others, based on those findings?

I think even for the first go around, they knew where the vaccine was needed. It’s mostly in the Northeast, the upper Midwest and the northern Pacific coast. Now one question is whether Lyme disease is expanding in its scope throughout the United States. There is some evidence that it is expanding slightly, but in general, those three regions have remained the same. It may be that there are micro-environments that the microbiota work can tell us more about in specific regions of Connecticut, but in a more global, epidemiologic sense, I don’t think that [information] would really change vaccine usage. So my feeling is that the market for Lyme disease may not have changed from the first vaccine. One thing about the first vaccine: It was available for adults. It wasn’t available yet for children. I find many parents, if they came to get a vaccine, would often say, “Okay, and vaccinate all of us.” [If you said], “Well, we can’t vaccinate your kid,” then they would say, “We’re not getting the vaccine if you can’t vaccinate the child.” It was an all or nothing phenomenon. So perhaps the presence of a pediatric vaccine might change things a bit. Second, with the first vaccine, it wasn’t clear at the time it

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was marketed how often it needed to be given, whether it was once a year, once every 2 years, once every 5 years, once every 10 years. People, I think, were a little concerned about how often they would need to take it. That perhaps made people a bit more reluctant. You might have to wait 10 years to figure out if you need to take it every 10 years. So, that’s an insurmountable bar. But overall, I don’t think that the market for a Lyme disease vaccine has changed dramatically since the first vaccine was out there. You’ve brought up a couple of points about families’ perspectives and different sociological or psychological factors that go into vaccination. I’m sure you are aware of recent media attention and skepticism of vaccines in general. I was wondering if you could comment on how you foresee vaccine development moving forward and how we need to think about things differently in the future to better communicate with the public about vaccination.

That’s a very important point. I wish I knew the answer to that. I don’t truly. I think if you look back at the history of medicine, it’s hard to say what the most important advances in medicine have been, but you could argue perhaps [that they are] hand-washing and vaccines. Certainly, vaccination has been shown to be arguably the most important thing in the past 200 years in the development of medicine. We have eradicated smallpox, polio has gone away, measles, mumps, rubella. We don’t even get the smallpox vaccine anymore because it’s gone, or at least mostly gone. Polio is still out there; it’s not gone yet. But you don’t see these diseases. You don’t see measles. The fact is that if the general public doesn’t see it, it doesn’t exist. It’s a hard thing to say, “It’s still out there, please take the vaccine.” The solution is not to bring back the diseases, but when the diseases were prevalent, people had a greater desire to get protected. The most important thing is to communicate that these diseases are still persistent and

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that you need to be protected. The second thing is, it’s important that if there are problems with vaccines, they be addressed. There was a link between vaccines and autism, and while those studies have been refuted both in the medical press and in the lay press, a little thing like that goes a long way to hurting vaccines. It takes a lot of effort by the scientific community and the public to just make the general public aware that those are fraudulent studies. When there are side effects, we need to know what they are and we need to be clear about that, but we need to get rid of the fear mongering and the false press. Again, it’s pretty naïve of me to say that’s just part of life and that’s a hard thing to overcome, particularly when wellknown politicians and celebrities make comments that are not based on good foundation. There is also the issue of herd immunity. If one person out of 1,000 or one child out of 1,000 doesn’t get vaccinated for measles, the community stays pretty safe. It doesn't make a difference. Two people probably doesn’t make a difference. But there is a tipping point. Once it gets to 100, or I don’t know the exact number, then measles becomes rampant again. Herd immunity is something that we think about from a societal point of view, whereas as an individual, it doesn't cross your mind.

There was a recent study conducted that investigated how we could better educate people who have a fear of vaccines or are against vaccines. The study found that no matter what type of material or how much material people were given, they were unable to change their views and, in fact, they strengthened their views in some sense. We think that’s scary. You can end up with an endemic.

What’s scary about that, too, is that that’s not a knowledge issue. The argument we were making before was that there wasn’t enough information for the public to make a rational decision. What you are saying is even a bit scarier. When presented with appropriate facts, an appropriate decision isn’t made. So that becomes more emo-

tional, a philosophical point of view either about society or about religion. Those are much more difficult things to overcome.

Where do you see the vaccine field moving forward? What challenges are facing scientists and physicians, and what would be a way to overcome some of those hurdles?

I think right now everybody would like an Ebola vaccine. Why is that? Because it’s in the news. Everybody would like a Chikungunya vaccine. Why? Because Chikungunya is a virus in the Caribbean. It might spread to North America. Despite the lack of those vaccines, vaccines are still being developed that are very useful. One of the most recent was the HPV vaccine, which is an outstanding vaccine. It has overcome different obstacles, some we haven’t talked about. Also, vaccines are changing a bit from infectious disease vaccines to vaccines in other fields: cancer vaccines, you have probably heard of those, [and] vaccines against other illnesses. Now, it might not be the same silver bullet. A smallpox vaccine pretty much targets smallpox. The cancer vaccines won’t be the same kind of thing. If some of those work partly, let’s say 20 percent, 30 percent, that might also change people’s perception about vaccines. Maybe in a good or bad way, I can’t really tell. If 80 percent of people got the vaccine and some got cancer, that might sway people against the vaccine. To me, the biggest concern are diseases that could use a vaccine. Three that come to my mind are tuberculosis, malaria, and HIV. Three illnesses for which treatment could be better, and cures are not available. Those diseases, in general, influence individuals from lower socioeconomic classes, so people can’t pay for the vaccines. Now who’s going to develop vaccines? Universities can do the theoretical work, the mechanistic work, the basic animal models, but vaccines are going to be developed by pharmaceutical companies to make a profit. Ultimately, pharmaceutical companies have to make a profit on their products to stay in business. So there is little motivation for vaccines against those lions. Dengue virus


[is] another one, possibly. I think in order to make vaccines for those things work, in addition to actually finding out the targets, which is not so easy, governments or large foundations need to become involved. The Gates Foundation is becoming involved, particularly for malaria. But without those types of efforts, I don’t see how you get a long-term economic plan that works for vaccines that primarily affect people in developing countries or in groups that are not really able to pay for their vaccines.

Do you think that targets for vaccines are going to be a little bit more surprising, the way that the Lyme vaccine target was surprising in hindsight? Do you think novel, unusual approaches might be more effective in some of these?

I can give you an example just for Lyme, in general. All vaccines target pathogen components: attenuated virus, recombinant protein, etc. They elicit some type of immune response, whether it be an antibody, virus’s CD8 T cells, innate immune activation, you can pick your thing. But it’s a specific immune response against a specific pathogen protein. There are two approaches that we are trying for Lyme or tick-borne illnesses. First, we are trying to make an anti-tick vaccine. There is work from 1938 by a professor, Bill Trager at Rockefeller, who showed if you put ticks on a guinea pig repeatedly, the guinea pig becomes tick immune. So the ticks will no longer feed on the guinea pig. And if you talk to older residents of Block Island, areas where there are lots of ticks, the older folks, particularly the ones who garden and spend their time in the woods or outside, will say, “Oh, I don’t worry about ticks. They don’t bite me.” I don’t have the data on that, but anecdotally, that’s what you hear. And I believe it. We have been able to reproduce tick immunity in guinea pigs in the laboratory.

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We can make guinea pigs tick immune. So the question is: What are the components of tick saliva that are inducing tick immunity? Usually what happens is the tick inserts its hypostome, and in a couple hours says, “Oh, I don't like this” and either pulls out the hypostome and goes away or it actually dies. If we can identify the components of tick saliva that induce the immune state that makes the guinea pig tick immune, we can prevent a tick from feeding. If you prevent a tick from feeding, then you can hypothetically prevent all tick-borne diseases, not just Lyme disease. Other animals, rabbits and so forth, develop tick immunity, too. Tick immunity is a known thing in different animals. Interestingly, the natural reservoir of the Lyme spirochete, which is the Peromyscus leucopus, the white footed mouse, does not become immune. So the animal that the tick feeds on and [that] the Borrelia, for the most part, lives in in nature does not develop tick immunity, which would make sense in evolutionary terms. Larger animals have a more substantial dermis, a more human-like dermis — mouse skin is quite different. Mice are not humans. This goes back to the earlier human to mouse, mouse to human study. But certainly if you can develop tick immunity, you can argue that you might be able to develop mosquito immunity. A tick feeds for 4 to 5 days, and a tick bite is painless. The tick hypostome is as sharp as an anopheles proboscis, so the ticks are making molecules that actually inhibit your pain response locally. A mosquito [bite] is a painful bite, which suggests that it doesn’t need to hang out for a long time. It relies on speed to get away. So mosquito immunity is not impossible, but it’s much more challenging than tick immunity. But there are sand flies, [and] there are a lot of different things that transmit diseases. So perhaps if we can work on ticks, we can extend that to at least some of the other vector-borne diseases. I don’t think that’s impossible.